1. Field of the Invention
The invention relates to a mechanism for releasing a prosthetic pylon/foot component from a lower limb prosthetic socket and, more particularly, to providing a quick-release for such a mechanism and method therefor.
2. Discussion of the Background
With the introduction of modular prosthetics in the mid-1990's, a number of conventional mechanisms have been designed to connect and to release a prosthetic pylon/foot component from the prosthetic socket of a user. In the lower limb prosthesis industry, a conventional link-plate is rigidly attached to the base of the socket, the link-plate typically has a downwardly extending pyramidal boss. A connector with an annular socket usually having four set screws couples to the pyramidal boss. The four set screws are adjusted and tightened, usually by a trained professional, to provide proper fitting for the prosthetic pylon/foot component. This is found, for example, in U.S. Pat. Nos. 3,659,294 and 6,458,163.
One prior approach for coupling to the pyramidal boss of the link-plate is set forth in U.S. Pat. No. 5,571,211 which provides a tubular adapter. The tubular adapter has the annular socket with four set screws for coupling to the pyramidal boss, a connecting sleeve with a formed axial slot between two outer tabs, and a plastic clamping cuff placed in an annular groove of the sleeve. When the tubular pylon of the prosthetic pylon/foot component is inserted in the sleeve, a clamping bolt engaging the two outer tabs is tightened to cause the plastic clamp to press against the inserted tubular pylon. The clamping bolt, outer tabs and plastic clamp provide a release mechanism requiring a separate tool for tightening and releasing. The tool is carried by the user.
A continuing need exists to improve such release mechanisms. For example, the simple act of putting on and taking off pants underscores the need for a lower limb prosthetic system wherein the pylon/foot component can be quickly removed so that the pants can be pulled over the socket and then reattaching the pylon/foot component to the socket through the leg of the pants. For active persons, a further need exists to quickly remove the prosthetic pylon/foot component to either attach a new prosthetic pylon/foot component (for the desired activity) or to adjust the present prosthetic pylon/foot component (such as for toe-in or toe-out). For example, users may require different pylon/foot components based on the activity, such as different feet with different shoes, wet-legs, running legs, climbing legs, riding legs, etc. By way of further example, when a user continually walks or walks uphill, the residual limb may tire from being at the same angle and/or pressure. The toe-in and toe-out can be adjusted to change the angle and/or pressure. Many other situations present themselves where releasing and removing/adjusting the pylon/foot component is advantageous to a user: sitting for extended periods of time, riding in a car, crawling, taking a shower, etc.
In situations where the pylon/foot component is frequently removed, a further need exists to provide a release mechanism that is durable. For example, in a situation where a prosthetic lower limb is reattached to the socket and a plastic part strips or fails, the user may be in a situation (such as out of doors, at a mall, etc.) where a replacement part is not available and the prosthetic lower limb is unable to be reattached. This presents a substantial inconvenience to the user. Some users also carry replacement parts with them in the event a failure occurs. A further need exists to provide an attachment mechanism which does not require the use of a special tool that would have to be also carried with the user.
The following patents provide release mechanisms not requiring a separate tool.
U.S. Pat. No. 4,564,365 discloses a quick change mechanism for a limb prosthesis requiring the use of two opposing cam latches located on opposite sides of a tubular member that allows the pylon/foot component to be released from the socket portion. This occurs by moving convex arches into and out of a recessed cylindrical area. A fail safe retainer clip engages the ends of the cam latches to prevent accidental release.
U.S. Pat. No. 4,938,775 recognized that the above '365 patent provided a complex design that was not strong enough for athletic activities and would require substantial modification for use with existing artificial legs. The '775 patent provides a first attaching member permanently attached to the lower end of the socket to releasably retain a second member on the removable support prosthesis. A handle is moved to engage and clamp the two mating members together. When the handle is raised, the attaching members release and the prosthesis can be removed. The '775 patent requires each different prosthetic pylon/foot component to have an attaching plate and a bearing attached to the upper end of the pylon. In use, the user must align and then seat the two attaching members together.
U.S. Pat. Nos. 5,928,290; 6,093,210; 6,235,062; and 6,402,789 provide a fastening device for a prosthesis to permit withdrawal of the cylindrical insert into an inclined washer fastening device.
British patent provisional specification No. 155,917 utilizes a sliding sleeve to lock a steel ball in a groove so that a prosthesis can be removed without use of tools.
In an entirely different technological area, quick-release mechanisms are conventionally used. For example, for bicycle seats, U.S. Pat. Nos. 6,581,492; 6,305,869; and 6,318,741 all relate to quick-release mechanisms. In another example for rotary die cutting, U.S. Pat. No. 4,054,394 discloses a curved lever arm shaped to conform to the contour of the circular head along with a spring clip to hold the lever in place to prevent accidental release.
A continuing need exists for a quick-release mechanism and method therefor for locking and releasing a prosthetic pylon/foot component from the socket without the use of a special tool. A further need exists for a quick-release mechanism which is simply constructed with few parts and which is durable for an active user. A need exists for a quick-release mechanism that does not require any alignment and seating of the locking mechanism, does not rotate when locked, and that does not require modification of the conventional prosthesis pylon of the pylon/foot component.